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2017 NABTEB GCE CHEMISTRY OBJ AND THEORY QUESTIONS AND ANSWERS SOLUTIONS – Nov/Dec Expo
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Exam Time: Thursday 30th Nov 2017
CHEMISTRY (Obj and Essay)
NABTEB GCE CHEMISTRY OBJ AND THEORY ANSWERS FROM EXAMCLASS.NET
In a degenerated orbital there are no two electrons that can have the same four
An ionic bond involves the loose and gain of electrons.
A covalent bond involves the sharing of electrons by two atoms where both atoms contribute.
A dativ bond involves sharing of electrons but only one atom contribute the electrons to be shared
Periodic law states that atoms are arranged in order Of increase in their atomic number
– Does not form common compounds – k10
– liberates hydrogen from cold water – J3
– Are halogens – N17
– Are in the same group – J31L13
– Forms ions by loss of three electrons – L13
– Ammonia – Triangular pyramid
– Methane – Tetrahedral
– sulphur (iv) oxide – linear
Allotropes are atoms of the same element in the same physical state but in different forms.
Diamond | Graphite
Transparent. | Blank
Very strong solid | Soft solid
Octahedral shape | Hexagonal shape
Diamond -> For cutting glass
For drilling limestones
Graphite -> For making pencils
For lubricating metals
An, electrolytic cell is made up of an electrolyte, electrodes and sources of electricity where the electrolyte decomposes.
2 Faraday deposits 63.5g of copper
i.e 2x96500c deposits 63.5g of copper
298,500c deposits Xg of copper
X = 298,500×63.5 / 2×96500
A reducing agent is the substance that is oxides in a redox reaction
They will turn purple permanent to pink.
– Pipeline product manufacturing company in portharcourt
– Dangote cement in lokoja
A saturated solution contains the maximum amount of solute that the solvent can take at a particular temperature.
A dilute solution contains more solution that solute contain at a temperature.
A super saturated solution contains more than enough solute than the solvent can contain at the temperature.
Chlorine – For killing micro organisms
Alum – For coagulation
It reacts with water to form acid
It changes blue litmus paper to red
It reacts with ammonia gas to form salt.
As an oxidising agent because it reduced to nitrogen gas.
As an acidic oxide because the product formed are salt and water only.
Disco sulphate(iii) acid – Hso2
(4dii) C2HSOH ——->CH3COOH+H20
C2HSOH ——-> C2H4+H20
Fractionating tower is the place where various fractions of crude oil are separated based on their boiling point
H–H- C – – C=C-4
The boiling point of the Alkanol is much higher even though the two compound are of similar relative molecular Mass. This is due to the presence of hydrogen bonds in butane. Although hydrogen bonds are not strong, much energy is still required to break them before the butan-1-ol molecules can escape as vapour
When a wine bottle is uncorked, its contents are exposed to air, causing them to oxidize. Bacteria naturally present in grapes can turn either the sugars in grape juice or the alcohol in wine into acetic acid, giving it a vinegar taste (and eventually producing a wine
(i)it is used for making vinegar
(ii) it is used as a laboratory reagent
(iii)it is used for coagulation of rubber from latex and casein(protein) from milk
Fat are solids usually of animal origin while Oils are liquid mainly from plants
Oils can be changed into fat by hydrogenation. Margarine is made by this process. Oils, usually from plants such as oil palm, groundnut and soybeans oil, are heated to about 180°C in the presence of finely divided nickel and hydrogen is bubbled in at about 5atm.The hydrogen is added across the double bonds in the saturated carbon chains in the oil. The hardened oils are then mixed with salt, vitamins, skimmed and various fats to form margarine
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